This invention relates to devices for safely lowering loads from substantial heights. In a preferred embodiment, it relates to compact portable devices which may be used to lower a person from an elevated location, such as a high-rise building, to the ground in an emergency.
The lowering of heavy objects from highly elevated levels to the ground is not an uncommon task. Of particular concern in recent years is the safety of persons on upper floors of high-rise buidings, such as apartments, office buildings, and hotels. In the event of a fire or other emergency, it is necessary for persons located on the upper stories of such buildings to make a rapid exit. In the event of a fire, normal escape routes within the building may be foreclosed, and conventional fire truck ladders have a limited vertical capability.
In the past, a number of different types of portable reel and line devices have been proposed which can be used by a person to lower himself to the ground by paying out the line or cable from the reel at a controlled rate. In general, these devices may be separated into two different groups; the first group retards the rate of descent by frictional braking means, and the second slows the descent by rotating a rigid member through a viscous liquid. Of this latter group, examples are found in Byrd, U.S. Pat. No. 3,847,377, Roper, U.S. Pat. No. 439,191, and Macfarlane, U.S. Pat. No. 4,088,201. Mechanical devices have proven generally unreliable; it has been quite difficult to properly adjust the particular degree of friction required to provide the desired rate of descent, and the quantity of heat generated in the mechanical devices has often been so great as to have a very substantial effect on the rate of descent, or even cause failure of the devices.
A substantially improved escape device is enclosed in the previously mentioned patent U.S. Pat. No. 4,088,201 to MacFarlane, one of the inventors herein. In that patent, a cable is wound about a spool which is enclosed within a casing. The casing includes an axially extended portion which houses a chamber containing a rotatable member in a viscous fluid. Rotation of the member in the fluid results in a frictional drag which controls the rate of descent of a person attached to the cable.
The present invention provides an improved design of a load descent device in which the rate of descent is controlled by rotation of a member in a viscous fluid. The present invention contemplates a highly efficient, inexpensively manufactured, and compact unit which has a virtually indefinite shelf life and is substantially fail-safe. The basic concept of the invention contemplates a housed spool having a hollow interior which forms a sealed, fluid-filled chamber. A series of parallel discs or plates are mounted within the chamber and are alternatingly rotatable or fixed. As cable is pulled from the housing, the spool rotates within the housing, turning the rotatable plates in the chamber. The close proximity of the movable and fixed plates within the chamber create substantial drag which is proportional to the speed of rotation of the spool. Accordingly, the viscosity of the fluid and spacing of the plates are chosen such that an average person will descend at a relatively uniform rate of about 4 feet per second.
Accordingly, it is an object of the present invention to provide a load descent device which is highly compact, and easily manufactured, yet is virtually foolproof. It is yet another object of the invention to provide an escape device which descends with the user so that it may be reused. It is yet another object of the invention to provide an escape device in which the cable cannot retreat into the interior of the housing, thereby causing jamming of the cable. These and other objects are effected by the device of the invention, a detailed description of an embodiment thereof being disclosed herein.